This invention relates generally to image reversal systems, and specifically to such systems which manipulate the input image to an electro-optic image recorder in such a manner as to allow selection of image output sense.
Every image exhibits a character relative to an object or original image which is referred to as its "sense". If, for instance, an image, in monochrome, corresponds point for point, black to black and white to white with the object, the image is said to be a positive. If, on the other hand, the colors are reversed, the image is a negative, or opposite in sense to the object.
Positive to negative, and vice versa, image conversion can be advantageously employed in a number of processes, including, for example, microfilm fabrication and duplication.
As mentioned above, the instant invention employs a broad class of imaging members which record optical images by an imagewise distribution of photo-generated voltages or current acting upon a voltage or current-alterable recording medium. Typically, in these members, imagewise activating radiation is spatially modulated at a favorable spatial frequency before it is incident on a photoconductor, which allows charge carriers to move in an external electric field. These charge carriers interact with a voltage or current-sensitive member which in turn modulates light.
U.S. Pat. No. 2,896,507 describes an imaging member which includes a photoconductive layer on a deformable layer sandwiched between a pair of electrodes, one of which is a thin metallic layer overlying the deformable layer. In operation, imagewise activating radiation is directed upon the member and an electrical field is established across the photoconductive and deformable layers thus causing these layers to deform in image configuration. The member is described as being capable of functioning as an image intensifier since the deformation image may then be read out with a high intensity light source and a Schlieren-type optical system.
Recently, a major advance in the art was made by Sheridon, who disclosed the Ruticon (derived from the Greek words "rutis" for wrinkle and "icon" for image) family of imaging members wherein the voltage-sensitive, light modulating recording medium comprises a deformable elastomer layer and a photoconductive material may be provided as a separate layer or incorporated in the elastomer layer. For a detailed description of the Ruticon devices, see IEEE Transactions on Electron Devices, Sept., 1972, and U.S. Pat. No. 3,716,359. Various different embodiments for establishing electric field across the elastomer layer are described. U.S. Pat. No. 3,716,359 is hereby expressly incorporated herein by reference for its teachings relating to recorder-structures and materials.
Image recorders within this broad class of imaging devices, including Ruticons, respond well to spatial frequency components of the image which lie within a given region and respond poorly to spatial frequencies which lie outside this region. In the normal course, when it is desired to obtain relatively uniform response to all spatial frequencies that lie within a relatively broad region the optical image is modulated at a spatial frequency that lies within the region of favorable response of the imaging device. Typically, this modulation is accomplished by inserting an optical screen, e.g., a Ronchi ruling, immediately adjacent the photoconductor.
Sheridan discloses (U.S. Pat. No. 3,716,359) several embodiments of electro-optical imaging members and several variations upon their useful application. The instant invention employs these members in a novel fashion to achieve image reversal.